Hypothesis Of Recruitment And Selection Free Essays

The replacement of the specialized species by closely related animals that possessed more flexible adaptations during a time of wide fluctuation in climate was a key piece of initial evidence that led to the variability selection hypothesis. Although Acheulean toolmaking hominins were able to cope with changing habitats throughout much of the Olorgesailie record, the Acheulean way of life disappeared from the region sometime between 500,000 and 300,000 years ago, perhaps also a casualty of strong environmental uncertainty and changing circumstances.

Hypothesis Of Recruitment And Selection

Hypothesis Test Selection Guide - SlideShare

A Bayesian would insist that you put in numbers just how likely you think the null hypothesis and various values of the alternative hypothesis are, before you do the experiment, and I'm not sure how that is supposed to work in practice for most experimental biology. But the general concept is a valuable one: as Carl Sagan summarized it, "Extraordinary claims require extraordinary evidence."

Hypothesis Test Selection Guide - Education

Now instead of testing 1000 plant extracts, imagine that you are testing just one. If you are testing it to see if it kills beetle larvae, you know (based on everything you know about plant and beetle biology) there's a pretty good chance it will work, so you can be pretty sure that a P value less than 0.05 is a true positive. But if you are testing that one plant extract to see if it grows hair, which you know is very unlikely (based on everything you know about plants and hair), a P value less than 0.05 is almost certainly a false positive. In other words, if you expect that the null hypothesis is probably true, a statistically significant result is probably a false positive. This is sad; the most exciting, amazing, unexpected results in your experiments are probably just your data trying to make you jump to ridiculous conclusions. You should require a much lower P value to reject a null hypothesis that you think is probably true.

HYPOTHESIS TESTS AND MODEL SELECTION - …

A different hypothesis is that the key events in human evolution were shaped not by any single type of habitat (e.g., grassland) or environmental trend (e.g., drying) but rather by environmental instability. This idea, developed by Dr. Rick Potts of the Human Origins Program, is called variability selection. This hypothesis calls attention to the variability observed in all environmental records and to the fact that the genus Homo was not limited to a single type of environment. Over the course of human evolution, human ancestors increased their ability to cope with changing habitats rather than specializing on a single type of environment. How did hominins evolve the ability to respond to shifting surroundings and new environmental conditions?

by the variability selection hypothesis

Three possible outcomes of population evolution in environmental dynamics typical of the Plio- (left). The ability to move and track habitat change geographically (narrow lines) or to expand the degree of adaptive versatility is important for any lineage to persist. Extinction occurs if species populations have specific dietary/habitat adaptations (i.e., a narrow band of ‘adaptive versatility’; highlighted bands) and cannot relocate to a favored habitat. In the hypothetical situation (right band) where adaptive versatility expands, migration and dispersal may occur independently of the timing and direction of environmental change. The evolution of adaptive versatility is the impetus behind the variability selection idea, which is explored later in this article.

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Another response to environmental change is to evolve structures and behaviors that can be used to cope with different environments. The selection of these structures and behaviors as a result of environmental instability is known as variability selection. This hypothesis differs from those based on consistent environmental trends. Environmental change in an overall direction leads to specializations for those specific conditions. But if the environment becomes highly variable, specializations for particular environments would be less advantageous than structures and behaviors that enable coping with changing and unpredictable conditions. Variability selection refers to the benefits conferred by variations in behavior that help organisms survive change. To test the variability selection hypothesis, and to compare it with habitat-specific hypotheses, Potts examined the hominin fossil record and the records of environmental change during the time of human evolution.

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Overall, the hominin fossil record and the environmental record show that hominins evolved during an environmentally variable time. Higher variability occurred as changes in seasonality produced large-scale environmental fluctuations over periods that often lasted tens of thousands of years. The variability selection hypothesis implies that human traits evolved over time because they enabled human ancestors to adjust to environmental uncertainty and change. The hypothesis addresses the matter of how, exactly, adaptability can evolve over time.

Hypothesis Testing: Fear No More

In literature, both terms are often used synonymously or interwoven. I am now trying to find a clear distinction between both terms. From my point of view, a hypothesis is usually expressed via a model. So even if we test a null vs. alternative hypothesis, from my perspective we are doing model selection. Can someone give me an intuitive description of this distinction?